Charlemagne was a Holy Roman Emperor, but the territory he ruled over isn't really the same entity as the Holy Roman Empire that would arise in the 10th century in the wake of the collapse of the eastern half of the Carolingian Empire. You can call Charlemagne, his son, and the later eastern Carolingians Holy Roman Emperors as that was, in fact, one of their titles, but the Empire is more associated with the Ottonians and on.

What Gama-rex said with the proviso that they didn't call it the Holy Roman Empire as yet. Charles was the Roman Emperor (the title was restored to usage) however Otto referred to himself as King of the Germans as did his successors for some time. Even when ruling in Italy and ignoring Germany (which was a mistake for the crown in the long run and led to ruinous accommodations with the German princes in return for their support for the crown or recognizing the heir apparent etc.

So in the end The Holy Roman Empire which was neither holy, roman or an empire wasn't holy, roman nor an empire when it started either. lol

King of the Germans